The present invention relates to the image formation system wherein the image receiving material is placed on the transfer drum, and the image forming material already subjected to development is placed opposite to said image receiving material to be pressurized and heated, thereby transferring the image of the image forming material onto the image receiving material.
According to the prior art in the field of printing plates, three-color or four-color dot film, for example, has been produced by color separation of the continuous tone image of the photographic original (e.g. negative film, reversal color film paper). This film is used to manufacture the printing plate such as PS plate. This method according to the prior art requires a great amount of film for color separation and image composition before producing printing plates. Such a complicated work process is accompanied by many errors including character and layout errors. Furthermore, it is necessary to provide some means for immediate response to the customer's requirements for changes in specifications. It is also necessary to make prior inspection to see if the printed matter can be finished to the required color tone, gradation and layout. Manufacture of a formal printing plate for this confirmation has required the process of trail proof called proof printing, as well as use of many other systems.
Images are produced, for example, by the dot film, CRT, silver salt such colored photosensitized material, non-silver salt based photosensitized material such as diazo compound, photoelectric system or image formation by dry toner, thereby estimating the quality of the completed printed matter. However, these proofing systems have generally required a long time to produce one proof sheet, involving such problems as large system size, expensive material costs and poor workability. These prior art systems have failed to meet all requirements for practical use.
In an effort to solve these problems, a proof system utilizing the photopolymer photosensitized material has been used in recent years to get proof sheets. This method uses the same pigment as the printing ink for color image, making it possible to produce multi-colored image considerably similar to the printed matter.
To make such a proof sheet, the image is exposed by the image exposure device by placing a color photosensitized sheet for Y, M, C and BK on top of the positive film corresponding to each color; then it is developed by a development device, thereby gaining the image forming material of various colors. After that, the image receiving material is placed on top of the first color image forming material by a transfer device, and is pressurized, heated and transferred, thereby transferring the image on the image receiving material. These operations are repeated four times for each image receiving material to get the multi-colored image.
When the colored proof sheet is prepared, the image forming material of each color is obtained by development of the image forming material having a colored photosensitized layer on the supporter after image exposure for example. Then the image receiving material is placed on the rotating transfer drum, and the developed image forming material is placed opposite to this image receiving material. It is pressurized and heated, thereby transferring the image of the image forming material onto the image receiving material.
The image forming material is set on the pin bar by the transfer drum setter, and is placed on the image receiving material. Since the rise in setter temperature makes it difficult for the user to set it, the user has to turn off the heat source and to wait for it to be cooled, according to the prior art method.
Just turning off the heat source and waiting for cooling require much time. Even of a cooling fan is used, the following problem occurs when the operation has been continued at a specified amount of air since power was turned on: Namely, much heat is dissipated only around the transfer drum setter, and only the setter temperature is lower by several degrees Celsius, even if the entire transfer drum temperature has reached the set value. Tens of minutes must be wasted to raise the setter temperature to the set value, while maintaining the temperature of other parts constant. Furthermore, if temperature is adjusted without stopping the transfer drum, for example, reduction in temperature of the setter alone may be prevented, but longer time is required for the entire transfer drum temperature to reach the set value.
Use of a cooling fan as the cooling means signifies blowing of cooling air into the setter for cooling. This will result in fluttering of the tip end where the image forming material is set on the pin bar, and setting difficulties will arise.
Furthermore, after the image forming material has been on the transfer drum setter, the pressure roller is moved while the rotating drum is turned, so that the image forming material is placed opposite to the image receiving material. Then pressurized and heat are given to transfer the image of the image forming material to the image receiving material. In order to prevent the pressure roller from contacting the setter in this case, the pressurized position is moved away from the setter, resulting in reduction of the effective image area that much. This problem has been involved in the prier art method.
To improve the image receiving material retainability, an adhesive sheet, for example, has been used on the surface of the transfer drum. The image receiving material is placed on this adhesive sheet, but dust may attach onto the adhesive sheet by use, giving adverse effect to the flatness of the image receiving material. To prevent this, the adhesive sheet must be cleaned to remove dust. Cleaning the sheet requires special measures to be taken; e.g. it requires heating of the transfer drum to be suspended or partial rotation to be adopted.
The transfer work of the drum transfer device is done manually; this requires much time and labor as well as a high degree of skill in ensuring high accuracy. The following is one of the method of setting the transfer film which is a image forming material; after the final printing paper and transfer film are put together, they are set on the drum. The tip of the transfer film is fixed on the drum, and the end of the transfer film is manually lifted to remove creases. Furthermore, it has been known that such conventional methods involve such problems as uneven transfer by uneven roller pressure or heat, transfer error of the transfer from the drum and a burn in handling the pin bar.
The present invention is intended to solve at least one of these problems. The object of the drum type transfer device according to the present invention is to provide a means for ensuring improved image quality by elimination of uneven transfer, improved image quality by eliminating transfer displacement, improved safety by eliminating the danger of being burnt; the present invention is, furthermore, intended to ensure workability improvement and prevention of operation errors.